This invention relates to a complex, vertical, magnetic recording medium comprising an underlayer of soft magnetic film with high permeability, and a recording medium layer provided on the underlayer, and more particularly to a complex, vertical, magnetic recording medium having improved recording and reproduction characteristics.
A complex, vertical, magnetic recording medium comprising an underlayer of soft magnetic film with high permeability, and a recording medium layer with perpendicular anisotropy, provided on the underlayer directly or indirectly via an intermediate layer, generates a higher reproduction output and requires a smaller recording current than a vertical, magnetic recording medium having no underlayer with high permeability. Namely, the former vertical, magnetic recording medium can be used with a high efficiency, and is practically the most preferable vertical magnetic recording medium. However, when a magnetic disc, which consists of a conventional, vertical, magnetic recording medium having a high permeability underlayer, is put into practical operation, the recording and reproduction characteristics thereof vary greatly as shown in FIG. 1 (which shows the envelope of the waveform of a reproduction output) during one turn of the disc due to the magnetic anisotropy of the underlayer. Therefore, such a magnetic disc cannot be used in practice. If the permeability of the underlayer is reduced to a low level, the magnetic anisotropy thereof becomes low, but the efficiency of the disc decreases. Consequently, providing the underlayer in the vertical, magnetic recording medium becomes meaningless.
Such a complex, vertical, magnetic recording medium as described above is disclosed in, for example, U.S. Pat. No. 4,210,946.